Direct Removal of Tritium from Mixture Gas by Alloy Getter with Functional Surfaces

氚和氘与氦和其他杂质共存于聚变反应堆堆芯废气中。从安全性评价和氚经济性的角度来看，从氦和其他气体中分离氚是一项重要的任务。利用低平衡氚压力的合金吸渣器直接脱除氚是一种安全、有效的分离氚的方法。然而，去除氚的效率可能会因氧和碳等杂质中毒而降低。本项目的目的是探索表面改性技术，以大幅度提高吸附剂的抗中毒耐久性。选用ZrNi作为模型材料。2001年采用化学镀技术进行了Pd涂层。将样品暴露于含有H_2O， CO_2和O_2的氩气中，在373 ~ 573 K温度范围内检测了氘吸收率的下降。在473 K以上涂覆Pd，可显著提高合金的耐中毒性能。应该强调的是，在573 K下，Pd涂层的样品没有观察到明显的降解，而没有Pd涂层的样品在暴露2小时后完全失活。2001年，人们的注意力集中在提高低温下的耐久性上。溅射沉积是一种新的Pd涂层技术。研究了暴露于空气后的活化行为，探讨了表面杂质对氢同位素吸收的影响。包覆Pd的试样在423 K真空加热活化，而未包覆Pd的试样则需要在873 K活化。结果表明，室温下Pd涂层试样表面未形成稳定的氧化物。因此，期望在低温下具有高耐久性。购买的质谱仪用于分析氩气、氘气和氢气中的杂质。

Tritium and deuterium coexist with helium and other impurities in exhaust gas from fusion reactor core. The separation of tritium from He and other gases is important task from the viewpoints of safety assessment and tritium economy. Direct removal of tritium by alloy getters with low equilibrium tritium pressure is safe and efficient method for tritium separation. The efficiency for tritium removal, however, can be degraded by poisoning by impurities such oxygen and carbon. The objective of the present project is to explore the surface modification technique to drastically improve the durability of getters against poisoning. ZrNi was selected as model material.Pd coating was carried out in 2001 with electroless plating technique. Specimen was exposed to argon gas containing H_2O, CO_2 and O_2, and degradation in deuterium absorption rate was examined at temperatures from 373 to 573 K. The durability against poisoning was significantly improved by Pd coating above 473 K. It should be emphasized that no significant degradation was observed for Pd coated specimen at 573 K, whereas the specimen without Pd coating was completely deactivated by 2 h exposure.In 2001, attention was focused on improvement of durability at lower temperatures. Sputter deposition was selected as new Pd coating technique. The activation behavior after exposure to air was examined to investigate the influence of surface impurities on absorption of hydrogen isotopes. The Pd coated specimen was activated by heating in vacuum at 423 K, whereas activation at 873 K was necessary for the specimen without Pd coating. This observation indicated that no stable oxide was formed at the surface of Pd coated specimen by exposure to air at room temperature. So, high durability at low temperature is expected.The mass analyzer purchased was used to analyze impurities in argon, deuterium and hydrogen gases.